Because it gets horribly fucky when you now have to figure out if a date is actually formatted as MM-DD-YY or DD-MM-YY.

Surely we've all handled reading an expiration date before and have wondered if we're eating something OK or has expired months ago because they chose the other format.

(Honestly, I think both formats are shit, and the only correct way to do dates with numbers only is YYYY-MM-DD. If not, then at least use letters for months, like 30 AUG 2023)